Research is underway in which the human electroretinogram and the visual evoked potential are recorded in response to alternating stimuli. Responses are recorded which result from stimulation of the peripheral retina as well as of the central regions. The methods may be used to obtain scotopic as well as photopic potentials, and current experiments are concerned with the Purkinje shift. Other stimulus variables are under examination including those of duration and luminance, movement, and color adaptation. An additivity model accounts for most current results.